The present invention relates to an electric braking apparatus which generates a braking force in a vehicle by a motor, and a vehicle on which the apparatus is mounted.
Heretofore, braking of a vehicle has been realized by multiplying a depressing force exerted on a pedal by a driver and transmitting the force to a hydraulic caliper of wheels by a hydraulic system. However, in recent years, owing to development of an electronic technology, a “by-wire” system is developed in which an amount of the pedal to be depressed is acquired by a sensor and an electric caliper electrically generates a braking force based on the amount.
In the by-wire system, hydraulic piping lines are abolished, and the braking force to be applied to the vehicle can freely be controlled in response to an electric signal. The electric caliper has therein a motor, and employs a constitution in which the motor is controlled to press a piston or a pad onto a rotor. The caliper sometimes has a parking brake (PKB) function of retaining a pressed state of the piston or the pad even in a non-energized state.
However, in order to correctly generate the braking force in the vehicle with the electric caliper constituted in this manner, it is indispensable to detect a pad contacting position in a state in which the PKB function is released. In general, since the pad contacting position constantly changes with a worn state or a thermally expanded state of the pad, the electric caliper requires a unit which detects the pad contacting position. To meet this requirement, a method of judging the pad contacting position with a current at a time when the pad is brought into contact at a constant speed (e.g., see US Patent Application Publication No. US2002/0027387) and a method of calculating the pad contacting position from a piston advancing position at a time when the constant current is passed (e.g., see Japanese Patent Application Laid-Open No. JP-A-2000-55094) are known.